Vitrified argillaceous product



Patented June 9, 1931 SU J TATE PATENT orrice new WILLIAM. B. PINE, or oxmuLann, OKLAHOMA, Ann .rosnrn n snaw, or STATE coL-f LEGE, AND MYRIL c. SHAW, or PITTSBURGH, PENNSYLVANIA, assrcmons or TWENTY PER CENT o can: :rosnrn B}. straw, TWENTY PER oEnT To earn MYRIL c. SHAW, AND SIXTY ran 01am To sagm T m:

VITBIFIE'D AneILLAcEoUs PRODUCT N'o Drawing. Original application filed November 4, 1929, Serial No. 404,863. plicatioii filed July 16, .1930. "Serial- No. 468,452.

The present invention relates to vitrified products produced by the direct manufacture from argillaceous materialssuch as clay and shale, by subjecting the said material 5 to compression and deformation (e. g. molding under pressure), whileat a temperature at which a substantial part (sa-y 20 to 35%) v of the argillaceous'material is actually in a fluid (i. e. fused) state. Thereby the solid p portions 'or particles of the material are forced into the liquid portions thereof, and whereby the latter is forced into the interstices between the solid unfused particles. This fused. portion,-upon subsequent cool- 5 ing becomes the binder tohold the article together.

vAn object of the invention is toproducc vitrified argillaceous products which are in some respects superior to any now known H) vitrified argillaceous products.

. A common way, and in fact the ordinary way of producing vitrified clay products heretofore, has been to mix the clay with water sufficiently to form a plastic mass, to 55 then mold the plastic mass in any desired manner either under pressure or not under pressure, then dry the same, and heat up to the vitrification range of temperature. Clay used for ceramic purposes is always a heterogeneous mixture. containing kaolinite or similar hydrous aluminum silicate and ma-- terials more readily fusible than kaolinite, and in many cases also'matcrials less readily fusible than kaolinite.

During the heating, the more readily fusible materials of course fuse first, and in the fused state these materials will perhaps react chemically more or less with constituents of the clay, and after the heating operation has been carried to a sufficiently high pointthe mass is allowed to cool whereupon the fused material solidifies into a. lassy or crystalline binder. The expression vitrification range used in the art at present, means that range of temperature through which Divided and this .ap-

certain portions of the clay mass will'fuse, without the entire material becoming fused. In fact in the manufacture of vitrified clay products, which have not become misshapen during the vitrifying operation, the mass never reaches the condition of being a viscous liquid, but does reach the stage ofbecoming substantially a plastic solid. v

For reasons of economy, we preferabl-yemploy clays, shales and the like, which contain Q5; more orlless iron. Most cla s and shales of the cheaper classes, will be ound to contain at-least 3 to 4% of iron, calculated as ferric oxide. Such clays, while unsuitable for use in makin porcelain, or white were '(on account of t e high iron content) are verysuitablcfor our process. We may add tov the raw clay, materials which will lower the vitrification ten'iperature of the mass. Thus we may add dolomite, magnesia or similar or. materials, up to 25 or even 30%. We may add slag (blast furnace slag etc.) up to 10-15% or other silicates such as feldspar up to 610%. These all act as fluxes at temperatures below that necessary for melting clays, even of the cheaper classes. These-gt ditions may be pure, but the cheaper im ure materials, being suitable, can be ,used. hey can be ground to a fine powder and wellmixed with the clay, in a preliminary opera tion. The amount of feldspar to be added or present should not be sufiicient t0 flux a large percentage of the, clay. Clay sometimes contains a, little undecomposed feldspar, as a natural constituent.

In the present process the temperature during the high temperature treatment will be substantially the same (or possibly a little higher than) the temperature, for that particular material. constituting the maximum ,5 temperature usable in the vitrification process of the prior art, for that particular material.

In accordance with'the present invention, the argillaceous material maybe preliminacrystals vor rily shaped or not as desired, and if preliminarily shaped this operation can be conducted in a wet or dry or semi-wet condition, as desired. The material is heated, either in a shaped condition or not, up to slightly below the P. C. E. (pyrometric cone equivalent) of that particular material, preferably not more than 100 C. below the value for the particular argillaceous material. The heatin may be conducted slowly or rapidly as desired, andthe heat canbe supplied in by combustion, electric furnace or in any 0t er way. The material is then ready for molding, shaping,,com-

passslng into the desired shape and size. hen the material has reached the temperature at which it is to be molded, the same will bea mixture of heterogeneous character, con- 1 taming '(a) solids, (b) viscous liquids and-- (c) liquids of relatively low viscosity. And considered as a mass, it is a plastic solid.

Clay is a heterogeneous mixture of different crystalline and amorphous materials. Under heat, new materials'will be formed by chemical reaction. As the temperature pr0- gres'ses,

to the freely liquid stateof' fusion. Other of these materials under heat have a ran e 3 of temperature over which they are high y= mold, and which, throughout the body of the viscous liquids.

:Any change whatsoever from solid to liquid state by heating accompanied by c0mpression while partly molten, results (up to a certain degree) in shrinkage in'volume, de-

crease in' porosity and increase in strength. These chan es are evidence of vitrification. Complete vitrification is followed at higher temperatures by fusing. and swelling produced by gases evolved or entrapped.

. At any given temperature a glven particle ln'the' mass, composed wholly of a given material will have equal fluidity throughout its mass. Difi'erent compounds (which may be not) will have diiierent viscosities at any given temperature. The viscosity of the whole clay mass at any given tent pe'rature, is the resultant viscosity of all the materials present.

In our process, soliclyat the hi ways relatively whole mass), so that the mass will scarcely flow under atmospheric pressure but the per cent of li uid is sufliciently high'to admit of pressing t e solids into the'liquid and to fill substantially all voids between the grains of solids to serve as a cementing medium, holding the grains of solids together and the whole forming a solid substantially impervlous' mass when cooled. At the'time when the per cent oi uniused h temperature stage, is althe material is to be pressed into shape, it should be about on the border line between 1 a'vei'y viscous liquid and a plastic solid, so

that at such temperature, the material will "fluids, at this stage.

a point is reached where certain of; these compounds are convertedfrom the solid iigh (say 65 to 80% of the only deform slightly, if at all, by the force of gravity, even if kept at that temperature for a considerable time, say 24 hours.

Atthis stage one should clearly distinguish low a plastic solid, namely, it is composed in major part (over and preferably to of solid particles,

mixed with ;a smaller amount of. *The mass is'then ready for moldin r The molds can be cold but are preferably hot, in order not to extract too much heat from the mass of material during the'early" stage of the moldin operation. If the mass has been heated in lmlk, it can be shoveled,-' raked or dropped at this stage, into a suitable mold, and then pressure applied for molding the material. ple); be applied by suitablerollers which compress the plastic solid material into thematerial, push the solid portions into the liquid portions of he mass and cause the liquid portions to flow into the voids, whereby the liquid portions become a binder; Or the pres-' sure could be applied by a rigid plunger. The jnressnre' also will force out gases which may he entrapped in the mass; The compression must be performed at the time when the ma-' terial contains a substantial amount (preferably over 20 or 25% but preferably not over 30%) of fused constituents. namely when the entire mass is in the condition of a plastic solid. I l

A plasticsolid is a material having such consistency that when pressure is applied to it, no deformation results until the pressure reaches :rcertaih value called-the yield point. For pressures above this valuethc'detorma tion is directly proportional'to pressure. A viscous liquid on the other hand does not require the initial pressure to start i'lciorngla tion. Deformation is directly '1uroportional' to ressure starting at zero. l 1 1 I call, attention to the feature that suitable metal rein forcemen'ts can be provided 'inyth'e mold before or during the step'of filling the mold with the m ateri'al, wher'eljxv a reinforced product will be produced. any of the ordi-' nary steel or iron in this process. with an enamel. 1 e I Samples of argill'ace'ous shale were ex,- amin-edin accordance witlith'cusual method of examination of=clay" and" shale to deterL.

reinforcements can be used These may first be coated The pressure? may (for examy Sample No. 1

Color Dark gray. Plasticity Good.

Absorpi Temp, v '01. ML deg. C. tion 5 shrink l Per cent Per cent Per cent 1000 34.1 20.4 1.4 1050 32.0 19.5 1100 31.7 10.1 i .85 1150 30.0 18.2 1 3.0 1200 27.0 15.7 g 5.5 1250 25.0 13.7 g 9.0 1300 11.4 5.5 .1 20.8 1350 2.7 1. 2 5 20.0

, Linear shrinkage: 5.5%.

P.. 0. E. .one 12 e (-1370" (3.).

Sample No. 2 Color: Light tan. Plasticity: Good.

deg. C. Family Lion i shrink Per cent Per arr/2t Per cent 1000 28.6 10.4 1050 29.4 16:8 1100 27. 7 15. 2 a. 1150 m 13.8 5.0 1200 10.0 10. 3 10.1 1250 15.0 7-.7. 14.1 1300 3.6 1.6 20.1; 1350 4.9 2.0 i -:1.0

Linear shrinkage: 7.5%. I

P. c. E. 0511514 -=141o (1.).

The data on these shales would be inter preted as representing material capable of producing a good face brick or hollow tile when treated in accordance with present standard practices in manufacturing these products (i. e. treated by the prior art).

We give the following experiments made on samples Nos. 1 and 2 respectively, in accordance with the present invention.

Example 1 The shale referred to in sample 1 above, was first crushed so that of the same would pass. through a 28 mesh screen, and the remaining 50% would pass through an 8 mesh screen but would be retained on e28 mesh screen. This material was then thoroughly mixed together and was very slightly moistened, and was then pressed into a briquet while moist. The material was then placed into a muffle of a furnace and was heated up to about 1270 0., (100 degrees below the P. C. E. value), at which point it was subjected to pressure by a heavy roller, was again heated to 1270 C. and again subjected to pressure by the roll, again reheated to 1270 C. and again subjected to pressure" by the roll. In this experiment the material cooled off substantially during each rolling, but the temperature at the time of rolling was close to 1270 C. During this 5011111 have been done in an'annealing leer;

operation the thickness of the hriquet was reduced about onethird. The product was then put back into the mufilc and the fire turned out to allow the muflle to cool slowly for" annealing the material. -(The anuealin The resulting product wasvan extremely hard, rock-like, strong, dense; vitreous material. The material is substantially free from bubbles and is substantially impervious. It is heavier than any product that could be made by previous processes from the same raw material (bulk specific gravity is here referred to); A broken surface of this prod uct shows complete vitrification and shows a stony fracture. This material being made from a mixture of coarse and fine particles,

- the coarse grains have not lost their identity although in some cases they have been distorted by the pressure.-

In this particular example the product was made from a mixture of coarse and fine material in equal volumes. However we call at tention to the fact that these proportions can varysubstantially or the process can be applied to the treatment of material all of which is fine".

Example 2 i I The material No. 2 referred to, all crushed to pass a 28 mesh screen was mixed with a little water and made into a rough tile. This was heated to 13509 C. degrees below the P. C. EQvalue), in the m'uflle (after-drying) and then was pressed between rollers three times as above indicated under Example I, then annealed. This clay had developed a decidedly vesicular structure during the. heating process and had swelled materially. This product was dense but decidedly vitreous in character, gas bubbles had been flat tened out to narrow slits by therolling proc 'ess. During the rolling operation the thick ness was decreased to about one-third of the original thickness. Such a material would be suitable for a beam or post, a railway tie brick or tile or paving material.

A particular utility of the product of the present invention is for the manufacture of paving bricks, and large pavi 11g units or sla.bs. Thus for instance it is'entirely feast ble to mold, by the'methods hereinabo've described. large slabs, say 5 to 10 feet square, reinforced or not as desired, which may be 5 to '10 inches thick. These can be readily manufactured and shipped'to the point of use. Also heavy building materials such as beams, terra-cotta, tiles, building blocks, railroad ties. curbstonemsidewalk slabs. large refractory blocks for refractory "purposes as for example glass making tanks, or glass melting tanks) can be made by'this process, any or all of which may be reinforced if desired. I

It is to be noted that-wedo not confine the as f invention to the making of slabs or blocks, but products of any desired shape can be made by this process.

An important feature of the present invention is the possibility of carrying out the process in a continuous manner, largely mechanically, thereby eliminating hand labor to a large extent.

()ne advantageous mode of carrying out the process is to heat the clay or shale or artificial mixture of or containing these materials, in a. rotary kiln, to the temperature at which it is to be compressed,and to then let it drop, from the lower end of such kiln, into a mold (which may be preheated or not) until a sullicient mass of the so heated material is in the mold, and to then compress the same in the mold, by a heavy roller or a plunger, or other similar device, after which the mold carrying the molded'article, or the said article alone, is passedintoand through a suitable annealing leer. I

Another important advantage is the fact that the process very greatly reduces the time necessary for producing a vitrified clay product, resulting ina materiallowering of the fuel required.

Reference has been made herein to having the material at temperatures well above the temperature of incipient vitrification of'the particular material, prior to compressing the same. This expression temperature of incipient vitrification of course refers to temperatures at which the material will commence to vitrify while the material is at atmospheric pressure. VVhensuch a material is subjected, at that temperature or slightly below to high pressure (several hundred or even several thousand pounds per square inch) in a mold, for a considerable period of time. vitrification takes place along with the shaping of the material. l

The compression, or molding under pressure, in the present invention, is effected within the vitrification range, ofthe particular material used. Furthermore the element of time during which pressure is applied, is not a factor in bringing aboutivitrification of the product. l

Thefunction of pressure in the present process is simply to shape the article and to compress the already hot material into a dense strong product.

We do not limit ourselves to the use of a. single clay or shale but wemay blend two or more clays or shales or add other materials than clay. The material at the. time of being compressed will be in the consistency of clay during the vitrification process ant not the consistency of glass during the blowing or casting process.

We may operate with high pressures at temperatures low in the vitrification range or with lower pressures at temperatures higher in the'vitrifioation range.

The finished product will be a vitrified ceramic product, not a glass. Fracture of the. product may be stony 0r vitreous.

While the rolling process is easily used and probably most desirable, we may use direct pressure at any angle or apply pressure by any suitable means.

We have referred above to metallic reinfol-cements of steel or iron. Other metallic pieces, such as copper wire or rods, brass, etc., may be introduced as electrical conductors.

The process, as herein described, and which ture of molding and the particular cla or These results are achieve be- I mixture used. cause when a clay product is produced under. the old processes, if it is fired to the point where a high percentage of the glass phase is formed, it invariably bloats, resulting in high porosity and it warps out ofshape resulting in misshaped articles. Byuse of this process the-pressure results in compressing the article into a smaller s ace, thereby.reducing the porosity and at t e same time correcting warpage and resulting in a perfectly shaped article.

Another highly important characteristic in which the new products difier from the old is in that cracks which sometimes develop in burning or drying and which are never healed in the old process, are by this new process completely eliminated and closed up.

Another characteristic wherein this process produces a new type of product is in that many clays contain minerals which disinte: grate or liberate gases (usually by. chemical action) during the firing process, resulting in a. weakening of the 7 structure becauseof either an expansion or a contraction. Such weaknesses are completely corrected by this new process by compressing the article after the disintegration has taken place resulting in a strong, dense body. These weaknesses are particularly apt toresult from the presonce of quartz or cyauite' and/or carbonates be formed into ing of voids, therefore resulting in I a. more perfect cementing of the whole body together.

Another condition in which this new product differs from anythingwhich can be made by present processes is in the uniform condition of products throu hout the thickness 0 massive bodies. Um or present burning processes when articles of great thickness, say 6 or 8 inches thick, are made, the interior of the body oxidizes and vitrities more slowly than the exterior. This results in the introduction of strains and also'in black cores in the middle of the piece. process massive pieces of sired can be reduced and sibility of bl ein'ding thin sections together by pressure the ultimate massive body will have the same hysical structure throughout its thickness because the heat will have perany thickness de formed this function-of vitrifying the body."

prior to the blending together'of the several sections and when they are thus pressed together all joints will disappearand the ultimate product will be uniform in color and density throughout its mass. I

The new product diflers from old products in that a raw material possessing no plasticity whatever (in the raw state) can a good product. The plasticity is an essential property in the molding of the prior processes in many cases, this product the property o'f'plasticity is o no consequence.

Finally, the ultimate shaped body, as to perfection of corners and edges and the straightness of sides when formed under this new process is absolutely perfect in so far as the mold shaping the article can be made perfeet, whereas under the old processes the product, being shaped previously to firing. invariably loses some of the perfection of its edges, corners and sides during the firing process because of unequal shrinkage in various parts resulting in products, which,-

(while passing inspection) are never entirely perfect.

We have referred above to adding various materials to the clay. The mixture, when subjected to the process of heating and molding, should contain at least -75% of actual clay, in all cases. We have referred above toadding a small percentage of dolomite, magnesia, chalk or slag. to the clay. Even when adding a small amount of one or several of these, to the clay the temperature necessary at the time 0t compression can be substantially lowered. Thus with such a shale as referred to in Example 1, the addition of about 10% of dolomite, will enable the process to be carried out at about 1170 (3., instead of 1270 C., as mentioned in said example. This effects a substantial saving in fue.

Reference is made to the fact that the products produced in accordance with the present process are superiorto those pro- Under the new because of the posp whereas in I f composed of an argillaceous mater al selected used. [The crease n the specifieagravity, ncrease n ,a

g a t asse in po o ty improvement embraces an 1nboth'astoopen f and closed pores), decrease inabsorpticmflny crease in. modulus of .rupture,-..1,ncrease}'mm toughness, decrease :in slag 'ienetrati'on and better maintenance ofltrue s standard method wetmolding, or pressnigi the ss-abu etc., drying sanie,stack1ng these in a kiln and slowly heating to within the vitrificationsaid. referred to r coi'isists Lin:

Mohs hardness, increase in parent specific- Leo range (this temperature depending on the:

articular, clay orlargillaceous material employed)f,-.sa dheat1n g requiring a long time,

tfrequently, several days or even severalweeks) after which the articles are allowed to s me did r g t e perature' stage, to 'prevent overheating, ingandisimilar defects in the product. hese de ectsare produced in. many cases byv gases liberated by chemical action of the ingredi ents, one upon another, of the clay or 'argillahigh ten); h sk frequently, produces cracks, swelling, warp .s lowl-yco ol; Greatcaremust beexercised in.

such standard ceous material. In ourprocess any-'gasesliberated are.

during the compression operation.

We claimz largely pressed outaof themass" ed compressed vitrified product:

from the herein descrihed groupconsis'ting.

tion of the said arg'illaceous material andthe RC. E. value thereof.

pe en ag of e y at too low to constitutea' material being com- ELAshap'ed compressed vitrified product composed of an argilhceousmaterial which lacks sufiicient feldspaf'and quartz in its composition to form a. porcelain, compressed into shape. while at a.temperature between the temperature ofjincipi'ent' vitrification of the said argillaceous material and the P. C. E.- value thereof.

3. A shaped compressed composed of an argillaceous material selected from the herein described group consisting of natural clays and shale; and mixturesthereof in which the percentage of easily fusible constituents is too'low to porcelain, and, such material being compressed into shape while at a temperature between the temperature of incipient vitrification of the said argilflaceous material and the metallic reinforcing member embedded in the mass.

vitrified product P. C. E. value thereof, and containing and 4. A shaped compressed vitrified product composed of an argillaceous material which lacks sufficient feldspar and quartz in its comconstitute a 51, I

position to form a porcelain, compressed into shape while at a temperature between the temperature of incipient vitrification of the said argillaceous material and then-P. C. 5 value thereof, and containing a metallic inset embedded in the mass.

5. A vitrified clay product in which the percentage of easily fusible constituents'is too low to constitute a porcelain, and having a 0 Mohs hardness higher than that of any heretofore known vitrified brick made from the same ole 6; A vitrified argillaceous product in which Y Y Y Y 1 I 1 Y the percentage of easily fusible constituents 1 i v i 5 is too low to constitute a porcelain, and. hav- Y ing about 10 13030 per cent of binding mate- I Y I Y y rial which has been fused and a percentage Y of pores less than the percentage of pores in any vitrified argillaceous product which could he produced from the same ar illaceous material by wet molding and v'itrifying by the standard method heretofore employed.

7. A structural material consisting of a metallic structural material imbedded in a molded vitrified argillaceous product, in

which the percentage of easily fusible constituents is too low to constitute a porcelain.

8. A vitrified argillaceous productin which the percentage of easily fusible constituents is too low to constitute a porcelain, and con- 4 ,taining an elongated metallic element 1mbedded therein. I Y

9. A molded vitrified argillaceous product, too poor in feldspar and quartz to constitute a porcelain, and being harder, stronger in tensi e and com ressive strength, tougher, more resistant to a rasion, denser, having a smaller percentage of pores, having a higher hulk specific (pravity, than could be produced in any pro not made from the same raw argillaceous material by wet molding, drying and vitrifying while unconfined. I

In testimony whereof we afiix our signatures.

' WILLIAM B. PINE. Y

JOSEPH B. SHAW. MYRIL G. SHAW. 

